Numerical simulation of the wide weak lensing survey with the Hubble volume simulation data

Figure 1

Figure 1 shows the lensing convergence map (of the fixed source redshift of 1) covering about one tenth of the whole sky (angular coverage of 0.8*pi/2 ster.).
The lensing convergence was obtained from the ray-tracing simulation combined with the Hubble volume simulation data, the largest N-body simulation in the world.
The Hubble "light cone" data (LCDM model) has an angular coverage of pi/2 ster., that is, the one eighth of the all sky with maximum redshift of 1.46 (corresponds to the radial comoving distance of 3000Mpc/h, the Hubble length, see the image of "PO" data on this web page).

Figure 2

Figure 2 is the zoom-in map of Figure 1. As Figure 2 clearly shows, the projected mass distribution observed via the WEAK GRAVITATIONAL LENSING is very smooth on the large scales with rare peaks (shown as a bright spots in the map) which may indicate the existence of the massive distant clusters of galaxies.

Figure 3

Zooming in the the 8.6x8.6 sq. degree filed enclosed by the white square in Figure 2. In Figure 3, one may find large-scale structures in the universe, e.g., large voids (dark color region), filament like structures and clustering of the bright peaks. The statistical properties of the lensing signal on the large scale, the so-called "cosmic shear statistics" can be used as a powerful tool of the cosmology.

Figure 4

Further zooming in the central 1.1x1.1 sq. degree filed of Figure 3 (the region enclosed by the white square in Figure 3). Figure 4 shows the lensing convergence map with the lensing shear being overlaid. The high lensing convergence signal in the center of this figure is caused by a massive distant cluster of galaxies. One may find clustering of the clusters as well as substructures in the clusters of galaxies. The lensing shear signal (which can be measured from images of the background galaxies) is used for reconstructing the projected mass profile of the clusters of galaxies. The lensing mass reconstruction method has a great advantage over other methods (dynamical methods or X-ray measurements) in that it does not rely on assumptions such like the dynamical equilibrium, isothermal and the spherical symmetry.

The lensing data set consists of 54 square fields. Each has 2048x2048 pixels with the pixel size of 0.25 arcmin, (Figure 3 is one of the fields). The lensing convergence and two components of the lensing shear are computed on each pixel.
If you are interested in using this data set for your research, let me know.

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Takashi Hamana
Last update: 04/02/2001